1. Field of the Invention
The present invention relates to improvements associated with a pair of pulleys used in a belt-and-pulley type continuously variable transmission.
2. Discussion of the Prior Art
As a continuously variable transmission, there is known a belt-and-pulley type continuously variable transmission which uses a pair of variable-diameter pulleys, which are connected by a transmission belt so that power is transmitted from one of the pulleys to the other. In a continuously variable transmission of this belt-and-pulley type, the effective diameters of the driving and driven pulleys are changed in the opposite directions, so that the speed ratio of the transmission is changed. Namely, the effective diameter of the driving pulley increases as that of the driven pulley decreases. Where the continuously variable transmission is used for motor vehicle, the transmission is required to have a high degree of durability. To this end, the transmission belt uses a multiplicity of V-blocks or other connecting members that are made of a relatively hard material such as metals and ceramics. The connecting members are disposed along the loop of the belt at a predetermined pitch or spacing. An example of this type of transmission belt is disclosed in U. S. Pat. No. 4,622,025.
Where the transmission belt employing the multiple V-blocks or other connecting members indicated above is used, the connecting members come into abutting contact with the contact surfaces of the driving and driven pulleys, at a relatively high speed, whereby the transmission tends to produce a comparatively high level of noises whose frequency increases wit the running speed of the vehicle, namely, with the rotating speed of the transmission belt, which determines the frequency at which the connecting members of the belt abut on the surfaces of the pulleys. Since the noise is associated with the spacing pitch of the connecting members, this noise will be referred to as "pitched" noise.